Refrigerator

ABSTRACT

This invention makes it possible to charge a refrigeration apparatus with the amount of refrigerant that the refrigeration apparatus requires at the time of onsite installation. As a result, the optimum refrigerant charging amount can always be obtained. The refrigeration apparatus is provided with a refrigeration cycle (A) in which an outdoor unit (X) equipped with a compressor ( 1 ), a condenser ( 2 ), and a receiver ( 3 ) and an indoor unit (Y) equipped with an expansion valve ( 4 ) and an evaporator ( 5 ) are connected together by a liquid pipe ( 8 ) and a gas pipe ( 9 ). The refrigeration cycle (A) is charged with refrigerant while a refrigerant charging operation state is created in which the liquid pipe ( 8 ) connecting the outdoor unit (X) to the indoor unit (Y) is filled with liquid refrigerant having a prescribed density. Refrigerant charging is ended at the point in time when, during said refrigerant charging operation, it is detected that the level (L) of the liquid inside the receiver ( 3 ) has reached a prescribed level (L 0 ).

TECHNICAL FIELD

[0001] The present invention relates to a split-type refrigerationapparatus. More specifically, the present invention relates to a methodof setting and determining the refrigerant charging amount when asplit-type refrigeration apparatus is charged with refrigerant onsite.

BACKGROUND ART

[0002] Split-type refrigeration apparatuses comprising an outdoor unitequipped with a compressor, a condenser, and a receiver and an indoorunit equipped with an expansion valve and an evaporator are well known.The refrigerant charging of split-type refrigeration apparatusesconfigured in this manner has conventionally been handled by chargingthe outdoor unit with a prescribed amount of refrigerant in advance andcharging additional refrigerant onsite in accordance with the length ofthe piping connecting the outdoor unit to the indoor unit when theapparatus is installed.

[0003] When the refrigerant charging amount is determined onsite duringinstallation, the performance and reliability of the equipment becomesdependent on the quality of the installation and, in some cases, themaximum capacity of the refrigeration apparatus cannot be realized.

DISCLOSURE OF THE INVENTION

[0004] The object of the present invention is to make it possible toalways obtain the optimum refrigerant charging amount by making itpossible to charge the amount of refrigerant that the refrigerationapparatus requires at the time of the onsite installation.

[0005] The refrigeration apparatus described in claim 1 is equipped witha refrigerant circuit—in which a compressor, a heat-source-side heatexchanger, a receiver, an expansion valve, a liquid pipe, autilization-side heat exchanger, and a gas pipe are connectedtogether—and a liquid level detecting means. The receiver collectsliquid refrigerant. The liquid pipe connects the receiver to theexpansion valve. The gas pipe connects the utilization-side heatexchanger to the compressor. The liquid level detecting means detects ifthe surface of the liquid inside the receiver has reached a prescribedlevel.

[0006] Since this refrigeration apparatus is equipped with a liquidlevel detecting means, it can be detected if the surface of the liquidinside the receiver has reached a prescribed level during refrigerantcharging operation when the refrigerant circuit is charged withrefrigerant.

[0007] Thus, for example, if the apparatus is configured such that itcan be detected when the liquid surface reaches a maximum liquid level(Lmax), then overcharging of refrigerant into the refrigerant circuitcan be detected. Furthermore, even when the length of the liquid pipe,gas pipe, and other connecting piping cannot be measured, the requiredamount of refrigerant charging can be obtained easily by detecting whena prescribed liquid level (L0) is obtained inside the receiver.

[0008] The refrigeration apparatus described in claim 2 is arefrigeration apparatus as recited in claim 1, wherein the liquid leveldetecting means comprises a bypass circuit and a temperature detectingmeans. The bypass circuit means connects the receiver and the suctionside of the compressor and includes an ON/OFF valve and a pressurereducing mechanism. The temperature detecting means detects thetemperature of the refrigerant flowing in the bypass circuit.

[0009] Since the liquid level detecting means of this refrigerationapparatus comprises a temperature detecting means and a bypass circuitthat includes an ON/OFF valve and a pressure reducing mechanism, theliquid level can be detected reliably at low cost.

[0010] The refrigeration apparatus described in claim 3 is arefrigeration apparatus as recited in claim 1 or 2, wherein thefollowing are further provided: a refrigerant charging operation controlmeans that executes charging of the refrigerant circuit with refrigerantwhile creating a refrigerant charging operation state in which theliquid pipe of the refrigerant circuit is filled with liquid refrigeranthaving a prescribed density; and a refrigerant charging ending meansthat ends the refrigerant charging executed by the refrigerant chargingoperation control means based on the detection signal from the liquidlevel detecting means.

[0011] With this refrigeration apparatus, the refrigerant circuit ischarged with refrigerant while a refrigerant charging operation state iscreated in which the refrigerant circuit is filled with liquidrefrigerant having a prescribed density. During this refrigerantcharging operation, refrigerant charging is ended when it is detectedthat the liquid surface inside the receiver has reached a prescribedlevel. Thus, the reliability of the refrigerant charging process isimproved.

[0012] The refrigeration apparatus described in claim 4 is arefrigeration apparatus as recited in claim 3, wherein theheat-source-side heat exchanger is an air-cooled heat exchanger thatuses air supplied from an outdoor fan as the heat source. Therefrigerant charging operation control means controls the outdoor fansuch that the condensation pressure of the heat-source-side heatexchanger (which acts as a condenser) achieves a prescribed value andcontrols the opening of the expansion valve such that a prescribeddegree of superheating can be imparted to the refrigerant at the outletof the utilization-side heat exchanger (which acts as an evaporator).

[0013] With this refrigeration apparatus, collection of more liquidrefrigerant than is necessary in the heat-source-side heat exchanger(which acts as the condenser) is avoided and the gas pipe disposedbetween the utilization-side heat exchanger and the suction side of thecompressor is filled With gaseous refrigerant. Therefore, a refrigerantcharging operation state in which the liquid piping is filled withliquid refrigerant having a prescribed density can be achieved easily.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0014]FIG. 1(a) is a block diagram showing the refrigeration circuit ofan embodiment of a refrigeration apparatus in accordance with thepresent invention.

[0015]FIG. 2 is an enlarged view of key components of the embodiment ofa refrigeration apparatus in accordance with the present invention.

[0016]FIG. 3 is an enlarged view of key components of another embodimentof a refrigeration apparatus in accordance with the present invention.

BEST MODES OF WORKING THE INVENTION

[0017] Below, preferred embodiments of the present invention aredescribed while referring to the attached drawings.

[0018] As shown in FIG. 1, this split-type refrigeration apparatuscomprises an outdoor unit X and an indoor unit Y. The outdoor unit isequipped with a compressor 1, an air-cooled condenser 2(heat-source-side heat exchanger) combined with an outdoor fan 6, and areceiver 3. The indoor unit is equipped with an expansion valve 4 and anevaporator 5 (utilization-side heat exchanger). The outdoor unit andindoor unit are connected by a liquid pipe 8 and a gas pipe 9 to form arefrigeration cycle A (refrigerant circuit). Liquid pipe 8 and gas pipe9 include an onsite piping section Z. Item 7 is an indoor fan.

[0019] As shown in FIG. 2, receiver 3 is equipped with a liquid leveldetecting means 10 that detects if the liquid surface level L hasreached a prescribed level L0 inside receiver 3. In this embodiment,liquid level detecting means 10 comprises a bypass circuit 14 and athermistor 15. The bypass circuit connects the prescribed level L0 inreceiver 3 with the suction pipe 11 of compressor 1 and has a solenoidON/OFF valve 12 that is actuated so as to open when the liquid level isdetected to be at the prescribed level and a capillary tube 13 that actsas a pressure reducing mechanism. The thermistor acts as a temperaturedetecting means that detects the temperature of the refrigerant flowingin bypass circuit 14. The prescribed level L0 is the surface level ofthe liquid refrigerant collected in receiver 2 when the refrigerant isneeded the least (i.e., when the amount of circulating refrigerant isthe smallest) during air-conditioning operation. The prescribed level isset such that the liquid level L inside receiver 3 does not fall below aminimum level Lmin when the refrigerant is needed the most (i.e., whenthe amount of circulating refrigerant is the largest) duringair-conditioning operation. Item 16 is a pressure sensor that detectsthe suction pressure.

[0020] Refrigeration cycle A is equipped with a controller 18 thatreceives detection signals from thermistor 15 and pressure sensor 16 andsends control signals to compressor 1, expansion valve 4, outdoor fan 6,indoor fan 7 and solenoid ON/OFF valve 12.

[0021] Controller 18 has a function whereby it acts as a refrigerantcharging operation control means that executes charging of refrigerationcycle A with refrigerant while creating a refrigerant charging operationstate in which liquid pipe 8 is filled with liquid refrigerant having aprescribed density and a function whereby it acts as a refrigerantcharging ending means that ends the refrigerant charging executed by therefrigerant charting operation control means based on the detectionsignal from liquid level detecting means 10. In the embodiment, therefrigerant charging operation control means controls outdoor fan 6 suchthat the condensation pressure at condenser 2 becomes a prescribed value(i.e., such that more liquid refrigerant than is necessary does notcollect in condenser 2) and controls the opening of expansion valve 4such that a prescribed degree of superheating can be imparted to therefrigerant at the outlet of evaporator 5 (i.e., such that the gas pipe9 disposed between evaporator 5 and compressor 1 is filled with gaseousrefrigerant). Here, the refrigerant is charged through a shut-off valve(not shown in the drawings) that connects the outdoor unit X to theonsite connection piping section Z.

[0022] Next, the operation of the refrigeration apparatus duringrefrigerant charging is explained.

[0023] The control signal from controller 18 controls outdoor fan 6 suchthat the condensation pressure at condenser 2 becomes a prescribed value(i.e., such that more liquid refrigerant than is necessary does notcollect in condenser 2) and controls the opening of expansion valve 4such that a prescribed degree of superheating can be imparted to therefrigerant at the outlet of evaporator 5 (i.e., such that the gas pipe9 disposed between evaporator 5 and compressor 1 is filled with gaseousrefrigerant). As a result, refrigeration cycle A is charged withrefrigerant while a refrigerant charging operation state exists in whichliquid pipe 8 is filled with liquid refrigerant having a prescribeddensity. During this charging, solenoid ON/OFF valve 12 is in the openedstate.

[0024] As the system is charged, the amount of refrigerant circulatingin refrigerant cycle A increases gradually and the liquid level L of therefrigerant inside receiver 3 rises. When the liquid level L reachesprescribed level L0, which is the inlet to bypass circuit 14, saturatedliquid refrigerant flows into bypass circuit 14. Up until this point,the saturated gas refrigerant filling the gas phase section of receiver3 was flowing into bypass circuit 14 and thermistor 15 was detecting thetemperature of this gaseous refrigerant.

[0025] When saturated liquid refrigerant flows into bypass circuit 14 asjust described, its pressure is reduced by capillary tube 13 and itevaporates, causing the temperature detected by thermistor 15 todecrease rapidly. Thus, the fact that the liquid level has reached theaforementioned prescribed level can be detected by detecting this rapiddecrease in temperature and refrigerant charging can be ended at thepoint in time when the liquid level is detected to be at the prescribedlevel.

[0026] With this method of refrigerant charging, refrigeration cycle Ais charged with the required amount of refrigerant. The required amountof refrigerant can be charged even if the length of the connecting pipescannot be measured onsite and the reliability of the equipment isimproved.

[0027] Furthermore, outdoor fan 6 is controlled such that thecondensation pressure at condenser 2 becomes a prescribed value (i.e.,such that more liquid refrigerant than is necessary does not collect incondenser 2) and the opening of expansion valve 4 is controlled suchthat a prescribed degree of superheating can be imparted to therefrigerant at the outlet of evaporator 5 (i.e., such that the gas pipe9 disposed between evaporator 5 and compressor 1 is filled with gaseousrefrigerant). As a result, a refrigerant charging operation state inwhich liquid pipe 8 is filled with liquid refrigerant having aprescribed density can be created easily.

[0028] In order to prevent degradation of the COP, it is critical toselect the capacity of receiver 3 such that refrigerant will notoverflow out of receiver 3 during the operating state in which theamount of surplus refrigerant is the most redundant, and with therefrigerant charging amount that was judged during the portion of theair-conditioning cycle when the liquid level L is the lowest (i.e., whenthe condensation pressure is high and the density of the liquid inliquid pipe 8 is large).

[0029] There are conventional refrigeration apparatuses that, as shownin FIG. 3, are provided with a bypass circuit 19 that connects the topedge part Lmax of receiver 3 with suction pipe 11 of compressor 1 andhas a solenoid ON/OFF valve 20 and a capillary tube 21. This bypasscircuit acts as a protection device during defrost operation, butrefrigerant overcharging can be detected by providing bypass circuit 19with a thermistor 22. In short, a thermistor 22 can be used to detect ifthe level L of the liquid refrigerant inside receiver 3 has reached amaximum level Lmax during test running after refrigerant charging. Inthis arrangement, a liquid surface sensor is used as the liquid leveldetecting means 10.

[0030] The embodiments presented herein were described regarding adedicated air-conditioning device, but the present invention can also beapplied to a refrigeration apparatus that is provided with a four-wayswitching valve on the discharge side of compressor 1 of outdoor unit Xso that the flow direction of the refrigerant in refrigeration cycle Acan be reversed and both heating and cooling can be performed.

INDUSTRIAL APPLICABILITY

[0031] This invention makes it possible to charge a refrigerationapparatus with the amount of refrigerant that the refrigerationapparatus requires at the time of onsite installation. As a result, theoptimum refrigerant charging amount can always be obtained.

1. A refrigeration apparatus equipped with a refrigerant circuit (A) inwhich the following are connected together: a compressor (1) thatcompresses gaseous refrigerant, a heat-source-side heat exchanger (2), areceiver (3) for collecting liquid refrigerant, an expansion valve (4),a liquid pipe (8) that connects the receiver (3) and the expansion valve(4), a utilization-side heat exchanger (5), and a gas pipe (9) thatconnects the utilization-side heat exchanger (5) and the compressor (1);and a liquid level detecting means (10) that detects if the surface (L)of the liquid inside the receiver (3) has reached a prescribed level(L0, Lmax).
 2. A refrigeration apparatus as recited in claim 1, whereinthe liquid level detecting means (10) comprises a bypass circuit (14)that connects the receiver (3) and the suction side of the compressor(1) and includes an ON/OFF valve (12) and a pressure reducing mechanism(13) and a temperature detecting means (15) that detects temperature ofthe refrigerant flowing in the bypass circuit (14).
 3. A refrigerationapparatus as recited in claim 1 or 2, wherein the following are furtherprovided: a refrigerant charging operation control means that executescharging of the refrigerant circuit (A) with refrigerant while creatinga refrigerant charging operation state in which the liquid pipe (8) ofthe refrigerant circuit (A) is filled with liquid refrigerant having aprescribed density; and a refrigerant charging ending means that endsrefrigerant charging by the refrigerant charging operation control meansbased on the detection signal from the liquid level detecting means(10).
 4. A refrigeration apparatus as recited in claim 3, wherein theheat-source-side heat exchanger (2) is an air-cooled heat exchanger thatuses air supplied from an outdoor fan (6) as the heat source; and therefrigerant charging operation control means controls the outdoor fan(6) such that the condensation pressure of the heat-source-side heatexchanger (2) (which acts as a condenser) achieves a prescribed valueand controls the opening of the expansion valve (4) such that aprescribed degree of superheating can be imparted to the refrigerant atthe outlet of the utilization-side heat exchanger (5) (which acts as anevaporator).